BRIGHTNORM,
According to the streamlight website:
http://www.streamlight.com/sl-series_specifications.htm
SL-20x
metal, 10 watt bulb
Run time 1.5 hours
SL-20XP
light weight polymer, 8 watt bulb
run time 1.5 hours
SL-20XP
light weight polymer, 3 watt bulb
run time 3.75 hours
Whoops, just re-read your question, and it is about the US vs the SL-20, 10 watt, but I will leave the info posted above for reference.
SL-20X™
Battery Nickel-cadmium 6 Volt, 2.4 amp hour, ½ D; rechargeable up to 1,000 times
Lamp 10 watt, hard glass halogen pre-focused in spun reflector
Material Machined aluminum anodized against corrosion inside and out; unbreakable polycarbonate lens.
Color Black
Weight (with battery) 1.9 pounds
Length 13 inches
Run Time 1.5 hours of continuous use between charges
Candlepower* Up to 30,000 pre-focused
Special Features 100V, 120V, 230V, or 240V AC or 12V DC chargers
UltraStinger™
Battery Nickle-cadmium 6 Volt, 1.8 amp hour, sub-C; rechargeable up to 1,000 times.
Bulb 6.3 Volt, 10 watt, xenon-halogen gas filled bi-pin.
Material Machined aluminum housing anodized against corrosion inside and out; unbreakable polycarbonate lens.
Color Black
Weight
(with battery) 1.1 lbs.
Length 11.75 inches
Run Time 1 hour of continuous use between chargers.
Candlepower* Up to 75,000
Special Features 100V, 120V, 230V or 240V AC, or 12V DC 10 hour charger.
So, the US is lighter and shorter than the SL-20x
I THINK (and I do not have the lights in front of me to look at) that the SL-20x is a wider light, whereas the US is more of a narrower beam